Spin coating, typically used to achieve nanometre thick films, is the established method for depositing perovskite precursors at lab scale for use in solar cells. This study investigates the dynamics of spin coating perovskite. By combining experimental measurement with a semi-empirical model the evaporation rate of the dimethylformamide solvent during the spin coating of a mixed lead halide precursor is determined to be 1.2 × 10^–8 m/s. When K-bar coating the same precursor the solvent does not significantly evaporate during the deposition process and when this film is crystallised on a hot plate a rough film results which gives a power conversion efficiency (PCE) of less than 2%. By increasing the airflow of the K-bar coated perovskite film during crystallisation to 2.7 × 10^–4 m/s the PCE increases significantly to 8.5% through an improvement in short-circuit current and fill factor.

This study investigates how the number and geographical distribution of solar installations may reduce aggregate irradiance variability and therefore lessen the overall impact of photovoltaic (PV) on grid distribution. The current distribution of UK solar farms is analysed. It is found that variability is linked to site clustering. Other factors may include distance and direction between sites, proximity to coast, local topography and weather patterns (i.e. wind, cloud etc.). These factors do not operate in isolation but form a complex and unpredictable system. The UK solar farm fleet currently comprises a range of system sizes which, when viewed en masse, reduces temporal variation in PV generation. The predominant southwest–northeast direction of solar farm groups is also beneficial in reducing output variability within grid supply point areas.

The energy yield of 15 different photovoltaic module technologies is measured during one year of operation at four locations (Germany, Italy, India, Arizona) corresponding to four different climate zones. The data are analysed in terms of a linear performance loss analysis for the module performance ratio (MPR) taking into account the influence of module temperature, low irradiance conditions, spectral and angular effects and soiling. This analysis is based on an independent characterisation of the modules in the laboratory combined with site specific data accumulated during operation. The model predicts trends of the measured MPR due to different module technologies and different locations.

Using a new improved harmony search-based hybrid firefly algorithm (IHBFA), a comprehensive controller gain parameter estimation of all distributed resources-based microgrid is proposed. To ensure a fast convergence and to endeavour less randomisation to conventional firefly algorithm (FA), diversity of population is increased by an improved harmony search (HS) algorithm. To decrease local optima searching delay, a linear incremental pitch adjustment rate and exponential decaying bandwidth is considered for proposed HS-based hybrid FA. Photovoltaic (PV), an auxiliary battery energy storage system (BESS) with the second-order phase-locked loop control, is considered as a primary DG (DG1) for the proposed microgrid. Padѐ approximation delay-based governor control is used for the diesel generator unit, considered as a secondary DG (DG2). The overall gain optimisation improves the dynamic stability limits by minimising low-frequency network behaviour. The effectiveness of proposed IHBFA in terms of power oscillation damping and improved stability limits is clearly demonstrated for microgrid applications.

The gearbox of a wind turbine involves multiple rotating components, each having a potential to be affected by a fault. Detecting weak faults of these components with traditional demodulation analysis is challenging. Multi-scale enveloping spectrogram (MuSEnS) decomposes a vibration signal into different frequency bands while simultaneously generating the corresponding envelope spectra. In this study, a MuSEnS-based diagnosis approach is applied to detect faults affecting the intermediate stage of a gearbox installed in an operating wind turbine. The MuSEnSs of 12 vibration channels have allowed to identify multiple fault features, including the weak fault of the big gear on the sun shaft. The effectiveness of the proposed fault diagnosis approach has been tested with industrial data and the faults themself have been confirmed with the disassembled gears.

This study deals with the voltage stability constrained optimal power flow (VSC-OPF) problem considering the wind power generation uncertainty. The main feature of the proposed model is to handle the uncertainty of multiple wind farms (WFs) in a way that for a given worsening of total cost, maximum tolerable uncertainty of wind power generation is achieved for all WFs. This maximum uncertainty is determined in a way that a required loading margin (LM), is preserved. It is worth noting that LM is the most important measure of voltage stability which reflects the distance from the current operating point to the voltage collapse point. For this aim, information gap decision theory (IGDT) is utilised to handle the uncertainty of wind power generation. The proposed model is implemented on IEEE 39-bus standard test system. In order to evaluate the effectiveness of the proposed VSC-OPF model for uncertainty handling of multiple WFs, the results obtained by IGDT technique are compared with Monte Carlo simulations and scenario-based approach. The simulation results imply that the uncertainty radius and the desired LM are inversely related, such that for a given tolerable increase of cost, the radius of uncertainty decreases by increasing the desired LM.

This study deals with the development of a proportional-resonant (PR) control applied on voltage regulation and harmonics compensation of a standalone self-excited induction generator (SEIG) for micro-hydro power generation system. The generation system considers: (i) a three-phase induction generator (IG) as SEIG, (ii) which is driven by an unregulated micro-hydro turbine, (iii) a three-phase three-legs distribution static synchronous compensator (DSTATCOM) and (iv) linear and non-linear loads connected to the AC bus. The voltage regulation is performed through the injection of reactive power to the AC bus through the DSTATCOM, providing excitation current to the IG. It is considered the employment of PR control techniques, which offers suitable voltage regulation through voltage harmonics compensation in the point of common coupling. Furthermore, frequency regulation is performed on the demand side by an electronic load control connected to the DC bus of the DSTATCOM. Experimental results were obtained to demonstrate the good performance of the voltage and frequency regulation, provided by the control system during transients of linear and non-linear loads.

Photovoltaic (PV) power generation levels in the three phases of a multilevel cascaded H-bridge (CHB) converter can be significantly unbalanced, owing to different irradiance levels and ambient temperatures over a large-scale solar PV power plant. Injection of a zero-sequence voltage is required to maintain three-phase balanced grid currents with unbalanced power generation. This study theoretically compares power balance capabilities of various zero-sequence injection methods based on two metrics which can be easily generalised for all CHB applications to PV systems. Experimental results based on a 430 V, 10 kW, three-phase, seven-level cascaded H-bridge converter prototype confirm superior performance of the optimal zero-sequence injection technique.

This study proposes a solar photovoltaic (SPV) water pumping system integrated with the single phase distribution system by utilising induction motor drive (IMD) with an intelligent power sharing concept. In addition to the power exchange from SPV to the IMD, a DC–DC boost converter is utilised as a power factor correction unit and a grid interfacing device. For good utilisation of SPV array, it is necessary to extract maximum power from the SPV array. To meet this objective, an incremental conductance based maximum power point tracking control is implemented. Whereas, to control the IMD tied to voltage source inverter, a simple voltage/frequency control technique is used. The proposed topology is designed and tested in the laboratory under standalone, grid interfaced and in mixed mode under various operating conditions.

Dwindling fossil fuel resources and concern of climate change resulting from the burning of fossil fuels have led to significant development of renewable energy in many countries. While renewable energy takes many forms, solar and wind resources are being harvested in commercial scale in many parts of the world. Government incentives such as renewable energy certificates and feed-in tariffs have contributed to the rapid uptake. In Australia many residential customers have taken up roof-top photo-voltaic (PV) systems. These residential PV generations are embedded in the low voltage (LV) networks that are not designed to take intermittent, two-way flow of electricity. Utility engineers are faced with the challenge of a legacy electricity distribution network to connect increasing amount of embedded PV generation. This study focuses on two aspects of the technical limitation – steady state voltage delivery and phase imbalance – and proposes how the technical limitations can be improved by optimising the existing voltage control schemes, the balancing of loads and generations between the supply phases, and finally the adoption of smart grid methodologies. This prioritised approach provides a cost effective means of addressing the impact of embedded PV generation. The proposed method is verified by computer simulation on a realistic LV distribution network in the state of Victoria, Australia.

Nowadays, expansion of new energy sources and the necessity of integrating them with the utility grid require more advanced power electronic converters. Matrix converters (MCs) and indirect matrix converters (IMCs) are recent solutions, which offer direct AC-to-AC conversion without the need for bulky capacitors. The main drawback associated to these converters is the limited voltage conversion ratio to 86.6%. Recently, many researchers focused on combination of the conventional IMCs and recently proposed Z-source (ZS) converters to attain higher voltage conversion ratios. The unique feature of the ZS converter is its ability to change the output voltage amplitude from zero to infinite, theoretically. Based on the previously proposed successful ZS converters, this study proposes a novel combination of two ZS networks with an IMC to achieve a very high voltage gain for practical application of integrating the renewable energy sources to the grid. Simulation results confirm the proper operation of the proposed combined converter topology.

Renewable energy systems such as photovoltaic (PV) and wind energy systems are widely designed grid connected or autonomous. This is a problem especially in small powerful system due to the restriction on the inverter markets. Inverters which are utilised in these kinds of energy systems operate on grid or off grid. In this study, a novel power management strategy has been developed by designing a wind-PV hybrid system to operate both as an autonomous system and as a grid-connected system. The inverter used in this study has been designed to operate both on-grid and off-grid. Due to the continuous demand for energy, gel batteries are used in the hybrid system. The designed Power Management Unit performs measurement from various points in the system and in accordance with this measurement; it provides an effective energy transfer to batteries, loads and grid. The designed control unit provided the opportunity to work more efficiently up to 10% rate.

Transmission expansion planning (TEP) is generally determined by peak demands. To improve the efficiency and sustainability of energy systems, attention has been paid to demand response programs (DRPs) and distributed generation (DG). DRPs and DG will also have significant impacts on the controllability and economics of power systems, from short-term scheduling to long-term planning. In this study, a non-linear economic design for responsive loads is introduced, based on the price flexibility of demand and the customers’ benefit function. Moreover, a probabilistic multi-objective TEP model which considers DRPs is also proposed. A probabilistic analysis method, the so-called Monte–Carlo simulation method, is implemented to handle the uncertainty of the loads, DRPs and DG in the TEP problems. Due to the problems’ non-convex formulations, a non-dominated sorting differential evolution program is used to solve the TEP problems. The proposed TEP model can find the optimal trade-off between transmission investment and demand response expenses. The planning methodology is then demonstrated on an IEEE 118-bus system in order to show the feasibility of the proposed algorithm.

This study presents a decoupled active and reactive power control technique, for a single-phase grid-tied inverter, using model predictive control (MPC). The proposed technique does not use conventional phase-locked loop, pulse-width modulation nor a synchronisation transform, which makes the control algorithm well suited for an all-digital implementation. The proposed controller minimises the number of switching state transitions required to control the grid-side current while simultaneously constraining the harmonics distortions and protecting the inverter from overcurrent condition. In this study, the switching frequency is reduced by using a look-up table to minimise the number of switching state transitions, which helps lowering down the switching losses. The proposed technique uses an adaptive weight factor which gives more priority to commanded power tracking during transient, and minimises the tracking error and switching frequency in steady state while constraining the harmonics distortion. This method improves the tracking performance as well as reduces the switching losses by minimising the switching frequency compared to the MPC with fixed weight factor and conventional decoupled power control. Thus, the outcome of proposed controller is a constraint multi-objective optimisation between the switching frequency reduction and grid-side current harmonics in terms of cost function with weighting factor.

Flyback inverter is known as a low cost solution for photovoltaic (PV) ac module application. This study presents a two-switch flyback inverter followed by a low frequency unfolding bridge for fractional horse power water pumping systems. This topology mitigates the problem of high-voltage transients at switch turn off which commonly exists in single switch flyback inverters. Moreover, the proposed control strategy achieves an integration of a novel sensorless maximum power point tracking (MPPT) algorithm as well as a constant v/f control for the efficient utilisation of both the PV panel and the motor. The proposed control algorithm minimises the cost and simplifies the control strategy. The validity and capability of the proposed method are verified by both simulation and practical results of a DSP-based two-switch flyback solar micro inverter for a fractional horsepower water pumping system.

This study proposes a hybrid intelligent method for short-term wind power forecasting and uncertainty analysis. In practice, the power output of a wind turbine is a direct function of wind speed. Owing to the intermittent and irregular nature of wind, the wind power generation is not easily dispatched and the prediction of wind power is highly uncertain. To allow a procedure for more accurate forecasting, a deterministic wind power prediction method that uses multiple support vector regression (SVR) models is established based on the wind power capacity and wind speed forecasts obtained from the Taiwan Central Weather Bureau (TCWB). An enhanced harmony search (EHS) algorithm is then used to estimate the parameters for each SVR model. To assess the risk that is associated with wind power forecasts in a power grid, an EHS-based quantile regression method that accurately reflects the confidence intervals for wind power forecasts is presented. The proposed approach provides wind power forecasts for future 3 h in steps of 15 min and the associated forecasting uncertainty. During testing on three practical wind power generation systems, the proposed method gives better forecasting accuracy and produces more reasonable confidence intervals than existing methods.

Grid synchronisation enhancement of a wind driven doubly fed induction generator (DFIG) using adaptive sliding mode control is described and evaluated in this study. The proposed scheme directly controls the stator terminal voltage of the DFIG to track the grid voltage without current control loop; hence, the structure of controller is simplified. For robustness of the control scheme, parametric uncertainty and external disturbances are included into the formed design procedure. A mathematical model of the DFIG as influenced by core-loss is considered to improve the theoretical prediction. Digital simulations are carried out to demonstrate the effectiveness and robustness of the proposed scheme using MATLAB/Simulink software package. Moreover, to validate the correctness and accuracy of the proposed schemes the calculated performances are compared with those results measured experimentally in the literature.

This study investigates a novel operating method of the interconnected power grid to improve dynamic stability using variable inertia control of large wind farms. In this scheme, the system inertia is considered as an adjustable operating parameter which can be regulated for inter-area power oscillation control and frequency support. Based on the linear state equations derived from a two-area interconnected power system, the effect of the controlled inertia on power oscillation damping is evaluated theoretically considering the different cases of power feeding and receiving networks. The respective wind turbine variable inertia control strategies for the feeding and receiving regional networks are proposed to enhance both inter-area power oscillation damping and frequency stability. A typical two-area interconnected power system with a high 30% wind penetration is simulated, which consists of four conventional power plants and two doubly fed induction generator (DFIG)-based wind farms. The results demonstrate that by using the proposed control scheme, the frequency stability and the inter-area oscillation damping are both significantly improved for the more effective inertia support in the interconnected power system.

As a small-scale power system, microgrid (MG) will lose support from the main grid if it switches to islanded mode because of the pre-planned scheduling or unplanned disturbances. To synchronise the frequency and voltage to their reference values, a secondary frequency and voltage cooperative control is proposed in this study. The proposed secondary control can synchronise the frequency and voltage to their reference values in finite time and achieve the active power sharing simultaneously. Moreover, it is suitable for switching communication architecture. The MG is considered as multi-agent systems and the system stability is proved by multi-agent theory and finite-time stability theory. A simulation system is established in Matlab/Simulink environment, and the results show the effectiveness of the proposed controller.

The constant voltage (CV) for maximum power point tracking (MPPT) technique is considered one of the most commonly used techniques in the photovoltaic (PV) applications. This study is aimed at proposing an adaptive reference voltage-based MPPT technique (ARV) to improve the performance of the CV technique by making it adaptable to weather conditions. The RV for MPPT is adapted according to the measured radiation and temperature levels. The operating range of the radiation at a given temperature is divided into number of divisions and the corresponding RV is recorded off-line in a truth table. The difference between the reference and measured PV voltages is compensated using proportional–integral controller to generate suitable duty ratio to the boost converter. Performance assessment of the CV technique after being improved covers time response, MPPT efficiency, oscillation and stability. The results present performance improvement by fast time response to reach steady-state value, more stable operation with no oscillation and high MPPT efficiency as compared with the CV technique without the proposed improvement.